Phenotypic trait variation in invasive and non-invasive alien species of Potamogeton in Kashmir Himalayan lakes of varying trophic status

Why some alien species become invasive and some of their phylogenetically related congeners do not, is still an intriguing question in invasion biology. Hence, we compared 15 quantitative traits between 4 species of genus Potamogeton, of which 3 (P. crispus, P. nodosus and P. natans) are invasive and one (P. perfoliatus) is non-invasive. Regression analyses of the selected quantitative traits, excluding the leaf number, petiole and peduncle length, showed a significant variation amongst the haplotypes of invasive and non-invasive Potamogeton. The invasive species consistently showed a higher degree of performance-related traits than those of non-invasive species. Phenotypic differentiation among populations was moderate to high (P-ST = 0.10 to 1.00). Bray-Curtis cluster analysis obtained from 11 populations of the 4 species revealed the maximum trait similarity between P. perfoliatus of Nilnag lake with that of Manasbal lake (similarity indices 0.0796), as against the distantly related invasive P. crispus and non-invasive P. perfoliatus of Manasbal lake (similarity indices 0.7689). We also studied occurrence of target species in three lakes (Dal lake, Manasbal lake and Nilnag lake) of Kashmir Himalaya along a gradient of trophic status. In general, the highest trait values for all the studied species were recorded in eutrophic Dal lake systems, while the smallest values were found in the oligotrophic Nilnag lake. Conclusively, 12 out of 15 quantitative traits showed significant variation between invasive and non-invasive alien species of Potamogeton, thereby providing useful clues for invasiveness of the 3 species (P. crispus, P. nodosus and P. natans) in a typical eutrophic Dal lake. However, other two lakes are likely to be invaded in view of being in trophic evolution from mesotrophic to eutrophic.